I need the definition of the term "exterior angle".
In geometry, an exterior angle is an angle that is formed by one side of a polygon and the extension of an adjacent side outside the polygon. The angle is formed by the two sides that meet at the vertex and is measured between the sides. The exterior angle is the supplementary angle to the interior angle, Exterior angles are used in geometry to determine the size of a polygon or a shape. They are also used to find the angles that are not visible from the outside of the polygon. Exterior angles can be found by subtracting the interior angles from 180 degrees.